Progress Levels are arbitrary measurements of how advanced a culture is, based on developments in technology and society. The concept was introduced in d20 Future, to describe both the level of technology in the campaign as well as the technology levels of other races comparative to the human one. Progress levels of six and higher were studied in d20 Future, with the default d20 Modern setting encompassing progress level five. In d20 Past, two progress levels are studied; Progress level three (the age of reason) and progress level four (the industrial revolution).

Skills and feats have deviated remarkably from their d20 Modern standards to accommodate for the differences in technology. For example, certain uses of a skill that were acceptable under a modern standard may no longer apply to a campaign setting where the technologies to perform these actions may not have been available. Similarly, some feats may represent modern knowledge or techniques that were not available to people centuries prior. It also includes new uses of skills and feats that might be more appropriate for a historic campaign.